PROJECT 4 ? PROJECT SUMMARY/ABSTRACT Epstein-Barr virus (EBV) is associated with 2% of human cancers, including a variety of B-cell lymphomas, nasopharyngeal carcinomas, and some gastric cancers. Over the current funding period, we developed a new epithelial cell line infected with EBV that can be used to identify factors that regulate the switch from latency to lytic infection that occurs during differentiation of epithelial cells. Using this and other EBV-infected cell lines, we identified multiple cellular factors that play key roles in determining whether EBV remains dormant or reactivates into lytic replication. We also discovered three novel classes of drugs (iron chelators, NEDDylation inhibitors, and immunomodulatory drugs such as pomalidomide) that induce reactivation of latent EBV into lytic replication, two of which are already FDA-approved for other uses. Based upon our findings, we hypothesize that p53 family members and NEDDylation are key contributors to regulation of the EBV latent-to-lytic switch. Here, we propose to test this hypothesis by determining: (i) the roles played by p53 (the most commonly mutated protein in cancers) and its close family member, ?Np63, in regulating EBV?s life cycle during differentiation of EBV-infected epithelial cells and treatment of these cells with drugs that induce lytic EBV replication; and (ii) how the NEDDylation inhibitor, MLN4924, and the iron chelator, deferoxamine, induce lytic EBV replication in cells latently infected with this virus. The information obtained from these experiments will then be used to identify optimal combinations of these drugs, together with other FDA- approved drugs, for efficiently inducing EBV into lytic infection in cancer cells in which it is latent. We are hopeful that these studies will lead to new lytic-induction therapies for treating patients with EBV-associated cancers.